The present invention relates to an improved metallic golf club head, and more particularly relates to improvements in weight distribution of a metallic golf club head such as an iron club head and a putter having a rear side recess.
Metallic golf clubs are roughly classified into two major categories, i.e. iron clubs and putters. In either case, efforts in production are much directed to stabilized course of travel to be traced by balls, increased distance of travel to be traced by balls and crisp feel at shot of balls.
In the case of iron golf clubs, the length of a club changes stepwise depending on the number of the club. That is, the longer is a club, the smaller is the number of the club. Long irons include Nos. 1 to 4 irons, middle irons include Nos. 5 to 7 irons and short irons include Nos. 8 to 10 irons. Usually, the course of travel traced by balls shot by an iron has its own bias according to its classified length. In case of a right-handed golfer, balls shot by long irons tends to follow rightward courses whereas balls shot by short irons tend to follow leftward courses.
In order to mitigate such bias in course of travel, it is proposed to bias the position of the center of gravity off the geometrical center of a golf club head. In the case of long irons, the center of gravity is biased towards the toe of the club head. Whereas, in the case of short irons, the center of gravity is biased towards the heel of the club head. More specifically, a recess is formed in the rear side of the main body of a club head and the position of the recess is biased towards the heel in the case of long irons and towards the toe in the case of short irons, thereby adjusting the position of the center of gravity.
In the case of this proposal, however, the depth of the rear side recess is limited from the viewpoint of the mechanical strength of the club head. Thus, adjustment in center of gravity cannot be practiced with full satisfaction. In other words, the course of travel to be traced by balls cannot be sufficiently stabilized. Further, presence of such a rear side recess reduces impact at shot of balls and, as a consequence, results in relatively short distance of travel to be traced by balls.
In addition to club heads fully made of metal such as cast iron and stainless steel, it is recently proposed to use so-called composite club heads in which metal is combined with highly elastic CFRP (carbon fiber reinforced plastics). One of such composite club heads is disclosed in Japanese Patent Application Sho. 60-214,297 filed on Sept. 27, 1985. In the case of this prior application, a recess is formed in the rear side of the main body of a metallic club head at a position corresponding to the club face and a CFRP backing is attached to the bottom of the rear side recess. A fastener ring is further set in the recess in order to fix the position of the CFRP backing. This composite construction is employed mainly for the purpose of reducing the weight of the club head. Lowering in mechanical strength due to presence of the rear side recess is made up for by attachment of the CFRP backing. Reduction in energy loss at impact assures increased distance of travel traced by balls and weight distribution towards the periphery of the main body enlarges the sweet spot of the club head.
The present invention relates to a further improvement of the club head of such a prior application.
In the case of putters, various constructions are proposed in order to provide a crisp impact and to stabilize the course of travel to be traced by balls. A toe-heel type putter is peripherally weighted so as to enlarge the sweet spot and thereby increase the inertial moment across the face of the club head. A cash-in type putter has its sweet spot focalized at the center of the main body rather than distributed across the face of the club head in order to assure crisp feel at shot of balls directly thereon. The enlarged sweet spot of the toe-heel type putter, however, tends to cause a dull feel at shot of balls. Whereas, the focalized sweet spot of the cash-in type putter cannot assure sufficiently stabilized course of travel to be traced by balls unless impact is made directly on the focalized sweet spot.
In addition to putters fully made of metal such as cast iron and stainless steel, it is also proposed to use so-called synthetic putters in which the main body of a putter is made of CFRP (carbon fiber reinforced plastic). Despite the merit of light weight, such synthetic putters cannot sufficiently assure stabilized course and increased distance of travel to be traced by balls and crisp feel at shot of balls.
The present invention relates to a further improvement of such synthetic putters.